There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e. without inserting a tube into the airway of the patient or surgically inserting a tracheal tube in their oesophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, which varies with the patient's respiratory cycle, to treat a medical disorder, such as sleep apnoea syndrome, in particular, obstructive sleep apnoea (OSA).
Non-invasive ventilation and pressure support therapies involve the placement of a patient interface device including a mask component on the face of a patient. The mask component may be, without limitation, a nasal mask that covers the patient's nose, a nasal pillow/cushion having nasal prongs that are received within the patient's nostrils, a nasal/oral mask that covers the nose and mouth, or a full face mask that covers the patient's face. The patient interface device interfaces between the ventilator or pressure support device and the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient.
Such devices are typically maintained on the face of a patient by headgear having one or more straps adapted to fit over/around the patient's head.
FIG. 1 shows a typical system to provide respiratory therapy to a patient. This system will be referred to in the description and claims as a “patient interface assembly”.
The system 2 includes a pressure generating device 4, a delivery conduit 16 coupled to an elbow connector 18, and a patient interface device 10. The pressure generating device 4 is structured to generate a flow of breathing gas and may include, without limitation, ventilators, constant pressure support devices (such as a continuous positive airway pressure device, or CPAP device), variable pressure devices, and auto-titration pressure support devices.
Delivery conduit 16 communicates the flow of breathing gas from pressure generating device 4 to patient interface device 10 through the elbow connector 18. The delivery conduit 16, elbow connector 18 and patient interface device 10 are often collectively referred to as a patient circuit.
The patient interface device includes a mask 12 in the form of a shell 15 and cushion 14, which in the exemplary embodiment is nasal and oral mask. However, any type of mask, such as a nasal-only mask, a nasal pillow/cushion or a full face mask, which facilitates the delivery of the flow of breathing gas to the airway of a patient, may be used as mask. The cushion 14 is made of a soft, flexible material, such as, without limitation, silicone, an appropriately soft thermoplastic elastomer, a closed cell foam, or any combination of such materials.
An opening in the shell 15, to which elbow connector 18 is coupled, allows the flow of breathing gas from pressure generating device 4 to be communicated to an interior space defined by the shell 15 and cushion 14, and then to the airway of a patient.
The patient interface assembly 10 also includes a headgear component 19, which in the illustrated embodiment is a two-point headgear. Headgear component 19 includes a first and a second strap 20, each of which is structured to be positioned on the side of the face of the patient above the patient's ear.
Headgear component 19 further includes a first and a second mask attachment element 22 to couple the end of one of the straps 20 to the respective side of mask 12.
A problem with this type, of assembly is that the headgear force vectors necessary to achieve a robust and stable seal against the face of the patient can cut a straight line near the corners of a patient's eyes, which can be uncomfortable and distracting.
One design of interface between the mask cushion and the patient is a seal flap. This provides a large contact area with the skin, and it is pressed against the patient by the pressure inside the mask volume.
However, locally high pressure areas can still result around the mask part, for example resulting from a reduced contact area if there is lifting of parts of the seal flap away from the contact with the skin.